EP241119a
GCN Circular 38281
Subject
EP241119a: EP detection of a fast X-ray transient
Date
2024-11-20T07:19:43Z (6 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
W. J. Zhang (NAO, CAS), Q. C. Shui (IHEP, CAS), H. Z. Wu (HUST), H. He, S. K. Yang (WHU), Y. L. Hua (PMO, CAS), W. Yuan (NAO, CAS) on behalf of the Einstein Probe team
We report on the detection of a fast X-ray transient, designated EP241119a, by the Wide-field X-ray Telescope (WXT) and confirmed by the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The transient was first detected with WXT at 2024-11-19 17:53:20 (UTC) and lasted for around 200 seconds. The WXT position of EP241119a is R.A.= 84.116 deg, DEC = 3.832 deg (J2000) with an uncertainty of 2.3 arcmin (radius, 90% C.L. statistical and systematic). It has a peak flux of ~4 x 10^-9 erg/s/cm^2 in the 0.5-4 keV band. The average 0.5-4 keV spectrum can be fitted with an absorbed power law with a photon index of 1.27(+0.45/-0.44) (with a column density fixed at the Galactic value of 2.1 x 10^21 cm^-2). The derived average unabsorbed 0.5-4 keV flux is 2.43(+0.67/-0.52) x 10^(-10) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.
At the detection of EP241119a EP was performing a calibration observation for FXT, during which the FXT automated follow-up mode was disabled. About 9 hours later a follow-up observation was carried out with FXT via ground-satellite command uplink. An uncataloged X-ray source was detected at R.A. = 84.1062 deg, DEC = 3.8404 deg (J2000) with an uncertainty of about 10 arcsecs (radius, 90% C.L. statistical and systematic), consistent with the position of the WXT transient within the uncertainties. The source flux is estimated to be around 2 x 10^(-13) erg/s/cm^2.
No previously known bright X-ray sources are found within the error circle around the source position. Further follow-up observations are encouraged to identify the nature of this X-ray transient.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
GCN Circular 38282
Subject
EP241119a: Global MASTER-Net observations report
Date
2024-11-20T08:00:28Z (6 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
legacy email
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko,
A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin,
V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP241119a ( EP Team et al., GCN 38281) errorbox 244 sec after notice time and 48684 sec after trigger time at 2024-11-20 07:24:44 UT, with upper limit up to 19.2 mag. The observations began at zenith distance = 39 deg. The sun altitude is -22.7 deg.
The galactic latitude b = -14 deg., longitude l = 201 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2677512
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
48715 | 2024-11-20 07:24:44 | MASTER-OAFA | (05h 35m 18.83s , +03d 37m 01.7s) | C | 60 | 19.2 |
49148 | 2024-11-20 07:31:58 | MASTER-OAFA | (05h 35m 18.82s , +03d 36m 20.2s) | C | 60 | 19.2 |
49349 | 2024-11-20 07:35:19 | MASTER-OAFA | (05h 35m 16.79s , +03d 35m 22.0s) | C | 60 | 19.2 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 38286
Subject
EP241119a : J-band observations with WINTER
Date
2024-11-20T21:47:58Z (6 months ago)
From
Tomas Ahumada Mena at Caltech <tahumada@caltech.edu>
Via
Web form
Tomas Ahumada (Caltech), Geoffrey Mo (MIT), Benjamin Schneider (MIT), Viraj Karambelkar (Caltech), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Mansi Kasliwal (Caltech), and Robert Simcoe (MIT) report:
We observed the field of the EP-WXT and EP-FXT X-ray transient EP241119a (Zhang et al., GCN 38281) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1 square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024).
Observations began at 2024-11-20T11:50:08.437 UTC (~18 hrs after the X-ray transient) and consisted of 30 x 120 s exposures. The images were processed using the WINTER data reduction pipeline (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565).
No source is detected in the FXT error region (Zhang et al., GCN 38281), setting a 5-sigma upper limit of 18.5 mag (AB) in the J band. We note there is a stellar object (18.99 AB mag in the SDSS r-band) within the 10 arcsec error region of the FXT localization.
WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.
GCN Circular 38288
Subject
EP241119a: GIT optical upper limits
Date
2024-11-21T08:04:26Z (6 months ago)
From
V. Swain at IIT Bombay <vishwajeet.s@iitb.ac.in>
Via
Web form
A. P. Saikia, T. Mohan, V. Swain, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team:
We observed the field of the X-ray transient EP241119a (Zhang et al., GCN 38281) with the 0.7m GROWTH-India Telescope (GIT). The observations started at 2024-11-20 19:32:58 UT, about 25.6 hours after the Einstein Probe trigger. We obtained multiple images of 300 sec each in the r' and i' filters. We did not detect any transient in our stacked image around the coordinates reported by the EP team (Zhang et al., GCN 38281). The obtained upper limits are:
| MJD (mid) | Filter | Exposure (s) | Limiting Magnitude (AB) |
| ------------- | ------ | ------------ | ----------------------- |
| 60634.8236018 | r' | 5x300 | 21.1 |
| 60634.8402112 | i' | 4x300 | 20.4 |
The magnitude is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our upper limits are consistent with others (Lipunov et al., GCN 38282; Ahumada et al., GCN 38286).
The GROWTH India Telescope (GIT, Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.
GCN Circular 38290
Subject
EP241119a: Optical upper limits with Kinder observations
Date
2024-11-21T15:34:14Z (6 months ago)
From
Janet Chen at National Central University <janetstars@gmail.com>
Via
Web form
A. Aryan, T.-W. Chen, W.-J. Hou (all NCU), A. K. H. Kong (NTHU), J. Gillanders (Oxford), S. J. Smartt (Oxford/QUB), Y. J. Yang, A. Sankar. K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, H.-C. Lin, C.-H. Lai, C.-S. Lin, H.-Y. Hsiao, J.-K. Guo (all NCU), L. L. Fan, S. Yang, Z. N. Wang, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report:
We observed the field of the fast X-ray transient EP241119a (Zhang et al., GCN 38281; Lipunov et al., GCN 38282; Ahumada et al., GCN 38286; Saikia et al., GCN 38288) using the 40cm SLT at the Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2024arXiv240609270C). The first SLT epoch of observations started at 17:07 UTC on 20th November 2024 (MJD 60634.713), 23.22 hr after the EP WXT trigger.
We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. We did not find any new and uncataloged optical source in the stacked frames within the 10 arcsecond error circle of the EP-FXT localization (Zhang et al., GCN 38281). However, we detected two SDSS sources within this error circle; they are both SDSS stellar sources. One is SDSS J053625.59+035023.6, reported by Ahumada et al. (GCN 38286) and the other one weakly detected is SDSS J053625.20+035021.4 with SDSS r_mag~21.97.
Moreover, we utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform aperture photometry on our stacked frames. The details of the observations and measured 3-sigma upper limit (in the AB system) are as follows:
----------------------------------------------------------------------------------------------------
Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass
SLT | r | 60634.713 | 23.22 | 300 * 21 | > 21.2 | 1".89 | 1.09
The presented magnitude was calibrated using the field stars from the Pan-STARRS1 catalog and was not corrected for the expected Galactic foreground extinction corresponding to a reddening of E(B-V) = 0.24 mag (AB) in the direction of the transient (Schlafly & Finkbeiner 2011).
GCN Circular 38610
Subject
EP241119a: 7DT Optical upper limits
Date
2024-12-18T08:33:49Z (5 months ago)
From
Gregory Paek at Seoul National University <gregorypaek94@gmail.com>
Via
Web form
Gregory S.H. Paek (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Hyeonho Choi (SNU ARC/SNU), Seo-Won Chang (SNU ARC/SNU), and Ji Hoon Kim (SNU ARC/SNU) report on behalf of the 7-Dimensional Telescope collaboration
We searched for the optical counterpart of the bright X-ray flare, EP241119a (Zhang et al., GCN #38281) using the 7-Dimensional Telescopes (7DT). Approximately 13.6 hours following the initial detection (2024-11-19T17:53:20 UTC), we targeted the localization center provided by the Wide-field X-ray Telescope (WXT) and confirmed by the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission at RA, Dec = 84.1062 deg, 3.8404 deg with an uncertainty of 10 arcsecs. Observations were made with thirteen 7DT units in twenty medium-band filters, denoted as m400, m425, then through m875, in which the numeric values indicate their central wavelengths in nanometers. Each medium-band filter has a bandwidth of 25nm. Observations for two broad-band filters were also carried out.
In the preliminary result, no significant transient event was identified. Photometric flux calibration was performed using synthetic photometries derived from the Gaia DR3 XP catalog (Gaia Collaboration et al. 2022) within the AB magnitude system. The 5-sigma upper limits (AB) range from 16.8 to 19.3 mag in the medium-band filters, reaching 20.1 mag in the g-band and 19.9 mag in the r-band. Observations were conducted under suboptimal conditions, potentially limiting our search sensitivity.
------
Filter Date-obs[UT] Exp.time[s] Depth(5sigma)
m400 2024-11-20T07:34:48 300 18.767
m425 2024-11-20T07:34:47 300 18.977
m450 2024-11-20T07:29:19 300 19.008
m475 2024-11-20T07:34:49 300 18.947
m500 2024-11-20T07:29:17 300 19.280
m525 2024-11-20T07:34:46 300 19.228
m550 2024-11-20T07:29:19 300 18.866
m575 2024-11-20T07:34:49 300 18.892
m600 2024-11-20T07:29:23 300 19.166
m625 2024-11-20T07:35:00 300 18.964
m650 2024-11-20T07:29:20 300 18.466
m675 2024-11-20T07:34:48 300 18.537
m700 2024-11-20T07:29:18 300 18.382
m725 2024-11-20T07:34:47 300 18.159
m750 2024-11-20T07:29:18 300 18.215
m775 2024-11-20T07:34:48 300 17.981
m800 2024-11-20T07:29:19 300 17.748
m825 2024-11-20T07:34:47 300 17.491
m850 2024-11-20T07:29:18 300 17.214
m875 2024-11-20T07:34:54 300 16.784
g 2024-11-20T07:29:19 300 20.120
r 2024-11-20T07:34:47 300 19.922
The 7-Dimensional Telescope (7DT), comprising 20 wide-field telescopes equipped with 40 medium-bandwidth (~25nm) filters located in Chile, aims to detect optical counterparts of GW sources and conduct the 7-Dimensional Sky Survey (7DS) of the Southern Hemisphere. Further information about the 7DT is available at http://gwuniverse.snu.ac.kr/.